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<br />Section 4 <br />4-40 Ramsey County Multijurisdictional Hazard Mitigation Plan | July 2012 <br />dam is an Ambersen concrete overflow structure, 574 feet long, hydro power station owned and operated <br />by Ford Motor Company located in St. Paul, MN next to Lock and Dam 1. The lock is 56 feet wide by <br />400 feet long. The dam was constructed in 1917, reconstructed in 1929, and the main lock was completed <br />in May 1932. The last major rehabilitation was done from 1978–1983. There is also a dam structure <br />(McKnight Basin Embankment) along McKnight Road that the Watershed District is required to have a <br />contingency plan in place for (Minnesota Statutes Chapter 112). The dam was constructed in 1981 and <br />came closest to breach in 1987 after an extreme rain event dropped 8 inches of rain in less than 5 hours. <br />Vulnerability Assessment <br />The probability of any dam failure or levee failure in the area is minimal. The low probability of an <br />incident suggests that the potential for impacts is minimal. Based on historical records from the past 75 <br />years, the probability of future dam and levee failure occurring in Ramsey County and the planning area <br />is considered low. <br />Assets Exposed to Hazard <br /> Property Risk/Vulnerability: It was determined that critical facilities as well as public, private, and <br />commercial properties are susceptible to being affected by a dam failure if they are located in the <br />inundation area. <br /> People Risk/Vulnerability: In evaluating vulnerability of the population in Ramsey County, it was <br />determined that people are vulnerable to the effects of dam failure through power outages, effects on <br />transportation routes, establishment of shelters, flooding, etc. <br /> Environment Risk/Vulnerability: Risks to the environment are high should a dam failure occur, <br />but the frequency of dam failures in Ramsey County is low. Environmental concerns would be <br />interruption of water supply, water contamination, and loss of properties. <br />Table 4-8 <br />Dam/Levee Classifications <br />Category Descriptions Quantity <br />Category I High hazard 1 <br />Damage Assessment <br />Because all facilities are subject to potential losses due to levy failure in affected areas, estimations were <br />done assuming 25 percent, 50 percent, 75 percent, and 100 percent damages. <br />Land Use and Development Trends <br />Future development throughout Ramsey County will result in the potential effects of dam failure. <br />Vulnerability <br />Dam/Levee Failure <br />Frequency of Occurrence Unlikely <br />Warning Time 3-6 Hours <br />Geographic Extent Community-wide <br />Potential Impact Major